Experiments will be done to elucidate the structure of the ribosome from E. coli and to relate that structure to its function in protein synthesis. Neutron scattering methods will be used to determine the positions of the 21 proteins in the 30S subunit of the ribosome. The mapping will be extended to include the positions of tRNAs in the A site and P site of the ribosome and to measure the relative positions of the large and small subunit. Nuclear magnetic resonance will be used to characterize one or more binding interactions involving ribosomal proteins and rRNA. Special attention will be given to 5S RNA and its specific binding proteins. The object is to identify the kinds of residues involved, the types of interactions and the source of specificity in these interactions. As an adjunct to these experiments; the RNAs and proteins used in the RNA-protein investigations will be used for crystallization experiments in an effort to open the way to the elucidation of their structures at high resolution. Protein synthesis is a fundamental metabolic process performed in essentially the same manner both in man and bacteria. Studies proposed above should contribute to our understanding of the mechanism of this process in all organisms by revealing the basis of the specific RNA-protein interactions on which the process depends and the geometry of the enzymatically active complex. Knowledge of this kind forms the infra structure on which future medical advances depend. More directly, knowledge of the details of bacterial ribosomes may be clinically relevant because many commonly used antibiotics act by blocking ribosomal steps in protein synthesis in bacteria.